The popularity of social networking via online networking sites/services is ever increasing. People may use social networking sites in various ways such as to keep in contact with friends, establish new relationships with others, post status updates, and share information such as, recommendations, pictures, and discussions with other people.
To establish relationships in social networks, users may send and receive invitations to become part of each other's network. When an invitation is accepted, the users become “friends” and may then communicate and share information. Unfortunately, this mechanism may be abused by attackers (e.g., spammers) who may establish accounts and send out invitations in bulk for illegitimate and/or undesirable purposes. The attackers often use attractive and familiar names that may mislead some of the invitees into accepting the invitations. Once the attacker and the victim invitee become friends, the attacker may engage in “spamming” by sending out unsolicited messages, posts, recommendations, and so forth. These unsolicited “spam” messages may contain malware, URLs to phishing sites, links to shady sites, unwanted commercial content, and/or other questionable material referred to collectively as spam messages or just spam. Consequently, one challenge that is faced by a provider seeking to maintain and/or increase the popularity of a social networking site is controlling unsolicited messages from spammers.